FACTSHEET 5: What is semantic dementia?

Frontotemporal dementia or FTD is a progressive disorder of the brain. It can affect behaviour, language skills and movement.

The main subtypes of FTD are called behavioural variant FTD and primary progressive aphasia or PPA.

PPA can be further split into two main subtypes, one of which is called semantic dementia or SD.

The first symptoms of SD are usually very subtle changes in finding words or understanding them. This is thought to be due to loss of semantic knowledge, our understanding of what things are or their meaning.

Symptoms can include:

Difficulty finding the right word
People may use another word instead of the correct one, for example saying ‘cat’ instead of ‘dog’, or calling something a ‘thing’ or other vague term.

Losing understanding of what words mean
People may ask the meaning of a word that they have previously known.

Talking about things in a vague manner
People may not seem to be making any sense when they speak.

Difficulty understanding what other people are saying
Sometimes this can be put down to people seeming to be ‘deaf’.

Problems with reading

Problems with spelling

People may initially complain that they have a memory problem or that they have forgotten words. However unlike in Alzheimer’s disease, day-to-day memory for events or the ability to find their way around are not usually affected in the early stages.

As the disease progresses other thinking problems may occur such as:

  • the inability to recognise objects
  • the inability to recognise faces
  • impairment of the memory for day-to-day events

Behavioural problems may also occur similar to those seen in behavioural variant FTD. In particular, people may:

  • behave inappropriately
  • become more obsessive or repetitive in their behaviour
  • develop a craving for sweet foods

See FACTSHEET 3 for more details on behavioural variant FTD.

Does SD run in families?

It is rare for SD to run in families. It usually occurs as a sporadic disorder without any genetic cause.

See FACTSHEET 2 for more details about familial FTD.

How is SD diagnosed?

Usually a diagnosis is made by a specialist rather than a GP. There is no single test that will make a diagnosis. A series of tests are usually performed including a scan of the brain. In SD the scan may show loss of cells in the middle of the brain in an area called the temporal lobe.

See FACTSHEET 11 for more details.

Is there a treatment for SD

There is currently no cure for SD but there are some important things which can help when caring for someone – see FACTSHEET 12 for more details.

The PPA Support Group has been set up to help people with PPA and their carers in the UK. It meets a number of times a year. More information can be found at www.ucl.ac.uk/drc/support-groups.

For a list of PPA support groups in the US and Canada see www.ppaconnection.org.